The goal of producing ultrasound contrast agents that include high impedance media has been achieved and reported by this group. The material consists of aqueous solutions of compounds used clinically, sodium citrate and calcium gluconate. These concentrate in the kidneys, permitting B-scans to be obtained, and require no lengthy preparation procedures prior to use. Early results using isolated kidneys, and renal artery administration to living animals have shown marked echogenic effect. This project will focus on experiments designed to address the following about these potential contrast agents: 1) Is the contrast effect of consistent intensity in a larger group of animals; 2) Can the effect also be measured in animals with induced renal infarcts; 3) Will the quantitative measurement of backscatter shown useful in a small series of animals prove useful in a larger series; 4) Can a cause/effect relationship between changing compound concentration at the tissue level and change in backscatter be demonstrated. The outlined goals will be accomplished by performing a group of experiments in dogs. Test kidneys exposed by laparotomy will be infused with a degassed medium containing sodium citrate in increasing concentrations. B-scan images will be obtained at baseline and at various points during the infusion. Control kidneys will receive degassed medium alone. The scans will be reviewed for increased contrast by a panel of trained observers. The imaging studies will be followed by a group of C-scans in excised kidneys using the same concentrations. These will relate quantitatively changes in backscatter to elapsed time. Results of these experiments will be compared with the B-scans to establish the utility of these quantitative measurements of backscatter. Another experiment will obtain autoradiographic data on the cause/effect relationship that may exist between the presence of the contrast agent in tissue and the corresponding ultrasound signal change. Systemic preclinical studies on ultrasound contrast agents have not previously been reported. This project proposes to evaluate the utility of sodium citrate and calcium gluconate as enhancers of backscatter in viable renal tissue. The project will serve as a template to unify the approach to performing future basic science ultrasound contrast agent studies.